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LT3476EUHF led-driver does not proper work

Hello Everyone,

We have developed our custom product in which we have been used the "LT3476EUHF" led-driver IC to control four illumination(RED,BLUE,GREEN.IR) LEDs of camera flash.

Now we are trying to control the individual led but as per our analysis driver is does not work properly.

We fixed the all 4-PWM to 60 micro-second ON-time and 40 micro-second OFF time and we are controlling the "Vadj1-4" using DAC IC where we had set range to 500mv. 

Now the individual and four LEDs are working good (not proper) but does not work twice or thrice at time so we need support to solve this issue as soon as posible.

Thanks & Best Regards,

Nikunj Patel
 



typo mistake
[edited by: Nikunj at 12:39 PM (GMT 0) on 17 Dec 2018]
Parents
  • The LT3476 can perform PWM dimming of the LED brightness but the LT3476 may not be able to achieve a "camera flash" as you mention.  To achieve PWM dimming of LED brightness, the LT3476 essentially turns the LED on and off repeatedly with a repetition period that usually is not longer than 10ms.  The duty cycle of the LED on-time determines the LED brightness.  For a camera flash, the LED is off for a relatively long time compared to 10ms used for PWM dimming and there may not be a definite period to the repetition of the LED on-time. 

    Did you use an example application circuit from the LT3476 datasheet or demonstration circuit DC976A as a starting point for your design?  I show the example application circuit from page one of the LT3476 datasheet in the image below.  The graph that is with the application circuit shows the example circuit is capable of turning the LED on for about 10us when PWM dimming.  Are you able to achieve 10us on-time performance similar to the example circuit I show below?

    LT3476 DS pg 1 app_1.png    

Reply
  • The LT3476 can perform PWM dimming of the LED brightness but the LT3476 may not be able to achieve a "camera flash" as you mention.  To achieve PWM dimming of LED brightness, the LT3476 essentially turns the LED on and off repeatedly with a repetition period that usually is not longer than 10ms.  The duty cycle of the LED on-time determines the LED brightness.  For a camera flash, the LED is off for a relatively long time compared to 10ms used for PWM dimming and there may not be a definite period to the repetition of the LED on-time. 

    Did you use an example application circuit from the LT3476 datasheet or demonstration circuit DC976A as a starting point for your design?  I show the example application circuit from page one of the LT3476 datasheet in the image below.  The graph that is with the application circuit shows the example circuit is capable of turning the LED on for about 10us when PWM dimming.  Are you able to achieve 10us on-time performance similar to the example circuit I show below?

    LT3476 DS pg 1 app_1.png    

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